Process of producing dual twist yarn



United States Patent Aaron Bnrleson, Burlington, N. C., assignor to Patentex, Inc., a corporation of New York Application February 8, 1956, Serial No. 564,127

6 Claims. (Cl. 57-157) No Drawing.

In my application Serial No. 524,394, filed July 26, 1955, I have disclosed a process for imparting left and right twists in alternating lengths of a single end of nylon yarn, which is adapted for use in the manufacture of stretchable fabrics, such as for example, ladies stretchable sheer stockings. The process involves, inter alia, heatsetting alternate sections of opposite twist in the yarn and backing out the twist.

The process of the present invention constitutes an improvement in the production of the aforesaid type of dual twist yarn in which alternate heat setting is not required, and conventional twisting equipment may be used in conjunction with suitable speed changing equipment to vary periodically the speed of the take-up roll onto which the previously twisted yarn is wound. By using yarn previ: ously twisted in one direction, maintaining the twister spindle at uniform speed and alternately slowing down and speeding up the rotation of the take-up roll, the yarn wound thereon will have successive lengths of alternate twists corresponding to the twist originally imparted to the yarn, and to the twist provided by this variable speed twisting operation, respectively.

The alternate twists are obtained by causing the takeup roll to rotate first relatively rapidly for a predetermined short length of time whereby the original twist is substantially retained in the length of yarn wound onto the takeup roll during this short period of time, that is, the yarn is drawn from the supply package and wound onto the take-up roll so quickly that there is very little opportunity for the original twist to be backed out. At the endof this time interval, the speed of rotation of the take-up roll is decreased sufiiciently to permit reverse twisting to take place, the original twist backed out and an opposite twist I imparted to the yarn. This reverse twisting operation continues for a period of time sufiicient to provide a length of reverse twisted yarn approximately equal to the length of yarn first wound and which has maintained its original twist. Thus, there are provided successive lengths o yarn of opposite twist in a single yarn end.

The complete process of my present invention may be carried out in several steps which include presetting the yarn at a suitable temperature, then twisting the yarn on a conventional uptwister to impart a suitable twist in one direction, next redrawing the twisted yarn onto a twister supply package, and then twisting the yarn from this package on a conventional twister while periodically varying the speed of winding up the yarn, as above described, to provide a yarn having alternate lengths of left and right twist. in the final twisting operation there is some unavoidable progressive variations of twist in relatively short end portions of the alternate left and right twist lengths. In other words, it is not practically possible to change directly or immediately from a left twist length to a right twist length, or vice versa. During the change-over or transition period, the twist previously imparted is backed out in the reverse direction to zero twist, and then prolgrtlalssively changed until the full opposite twist is estabis ed.

However, the process of the present invention constitutes a marked improvement over other possible procedures in that it limits this change-over length to a minimum so that it is relatively very short as compared with the lengths of left and right twist that occur adjacent this short changeover length. For example, typical left twist and right twist lengths would be 70 to inches and such lengths connected by a change-over length of only about 9 inches. By limiting this change-over length of yarn to a few inches, the stockings or other stretchable fabrics knitted from the yarn are substantially free of any apparent defects due to the short length of varying twists.

The significance of this short transition or change-over length of yarn may be more fully realized by comparison with dual torque yarn produced by a different procedure, such as, for example, the stopping and reversing of a motor that might be used to drive the twister spindle. In that case, any attempted abrupt stopping and reversing of the motor might soon result in damage or destruction of the motor, and if the motor were permitted to override after cutting off the current or applying a brake in the usual manner, the length of yarn which would accumulate during this change-over period would be quite substantial, such as, for example, several yards in length. If yarn of that nature were used for forming the stretchable stocking or fabric, the long length of yarn having a variable or progressive changing twist would produce easily apparent defects in the finished product. Also, yarn prepared in this manner, using a reversing motor, would normally result in a yarn having difierent torques but not different twists, and therefore having substantially less of the liveliness needed for producing stretchable and retractable fab- IICS.

The process of the present invention is particularly characterized by producing a single end of yarn which has periodically occurring throughout the length of the yarn, sections or lengths of opposite twists and with very limited or short sections of varying twist-s interposed between the opposite twist sections.

A specific but non-limiting example of the complete preparation of the above described dual twist yarn of this invention, including the steps of presetting, original twist ing, and periodic reverse twisting, is as follows: Monofilament, l5 denier nylon yarn is heat set to stabilize the twist subsequently inserted. The heat setting may be obtained by exposing the yarn to wet heat, e. g. steam or hot water, for a time suflicient to effect the desired heat-setting. Typically suitable setting operations involve subjecting the yarn to either steam at a temperature within the range of 220 to 270 F. for a period of time between 15 and 60 minutes, or hot water at a temperature of from to 212 F. for between 10 to 60 minutes. Also the yarn may be set with dry heat, e. g. by using a heated metal plate or like member which contacts the yarn for the necessary length of time. A metal plate heated to from 220 to 450 F. and in contact with the yarn for A second to /2 minute, and preferably 1', second, gives satisfactory setting.

After heat setting the yarn is wound on a twister supply bobbin and placed on a conventional uptwister machine, such as, for example, the Acme machine No. T. P. D. 2446, manufactured by U. S. Textile Machine Co., Scranton, Pennsylvania. The yarn is uptwisted on this machine in a 2 (left) direction so as to impart to the yarn 25 turns per inch left twist. In this operation the spindle speed of the machine is 12,500 R. P. M., and the yarn take-up speed is 500 inches per minute.

Following this initial twisting operation the heat-set, twisted yarn is redrawn from the take-up shaft onto a twister supply package and the latter is then placed on the same, or similar, uptwister machine having a spindle speed of 12,500 R. P. M. The yam take-up or wind-up roll of this machine is rotated at a high speed, i. e. 304 R. P. M.,

such that approximately 72 inches of yarn is taken up on this roll in 1.728 seconds. This particular operation will remove approximately 5 turns of the original 25 turns ei; twi t in the ya n, ea in .20 turns ef is in th rst l ngth o yar I ol ow nghe Produ ti n o t i fi st en h o 7, inches 015.29 turn le t wi y r th speed f h t ke up r l is educed fr m the or gi l hig pee bo e-ment oned, of 304' R- t a o spe ef 22-6 R- .P-

throu uitable speed red c n mec a isms so a to inser o p uee a righ i t o tu n n t e next length of yarn,

. @2172 in hes o Yet Th s e e d i n p e e r step, to impar n t e 2. urns i t tw s i t e se nd s ue ess vell es h 9t 7 i che o the ya n, qui e .5.5 se onds a th redu ed ope at n speed f the takeme L lt i n eessery to t t th ya n th above sp fiesl 45 illE t9 the r ght n rde t remeve the 25 turns f lef t is d ree n a d'build up r nser 20 t ns of right twist direction in this length of the yarn.

The above d cr bed yele of p at o o th t -1 p 1 firs a e rapid p d and hen eta u ste ie l r ducedtspee d, is repeated so as to produce on the take-up 'roll a continuous desired length of the dual twist yarn thalic acid and ethylene glycol (Dacron) or a vinylchlo ride-acrylonitrile polymer (Dyncl) may also be processed in the manner described herein.

Similarly, the invention is broadly applicable to the production of all types of woven and knitted fabrics in which stretchability is desired, e. g., knitted underwear, sweaters and bathing suits. One of the more important applications of the invention, however, is in the processing of I monofilament nylon yarns, for example l0, 12 or 15 denier The method of this invention is applicable to both 'monofilament and multifilament yarns and the selection thereof depends principally upon the end-use of the yarn.

Fortexarnple, the leg portion of a ladies sheer stretchable stocking would normally be produced from monof lament ya n, he e he t Pe t en of t king oul lly be pre ue d f em mu tifi emen ye n- Il u a bu men-l mi n ex mp es o ya n .den ers an o e pond ing twists to be produced in the yarn in accordance with the foregoing method, for monofilament and multifilamerit yarns respectively, are as follows:

Yarn Denier g 5 53 It is to be understood the present process is not limited to anyof these yarn deniers, types, or twists, and may be used in various other combination.

The yarn produced by the process of this invention will have alternate sections or lengths of right twist and left twist of any desired length, and successive sections of different twists will be separated by relatively very short monofilament yarn, for use in making full fashioned and/ r seamless hosieryl Obviously various modifications may be made in the invention as described herein without deviating from the scope thereof as defined in the appended claims where- I claim:

1. A process of producing dual twist nylon yarn comprising twisting nylon yarn in one direction to insert,

therein a desired number .of turns twist throughout the length of the yarn, next twisting said yarn in the opposite direction whilewinding up said' yarn at a sufficiently rapid rate to avoid substantial reverse twisting for a given length of the yarn, and then continuing said reverse twisting and winding up said yarn at a sufiiciently slow rate to impart an opposite twist in the next succeeding length of yarn.

ZIAprocess for producing alternating sections of opposite twist in a thermoplastic yarn, comprising twisting a thermoplastic yarn having substantially no twist a pre; determined number of turns per inch in one direction throughout the length of said yarn, and thereafter twist- 7 ing said yarn in the opposite direction while winding said yarn first at a high speed for a predetermined length of time, and then at a low speed for a predetermined length fiime- 3 A process as defined in claim 1 and in which the References Cited in the file of this patent UNITED STA ES P E 2,061,614 Dickieet al. Nov. 24, 1936 2,089,193 Dreyfus Aug. 10, 1937 2,465,996 Bloch Apr. 5, 1949 2,564,245 Billion Apr. 14, 1951 2,585,518 Valentin Feb. 12, 1952 2,715,309

Rosenstein et a1 Aug. 16, 1955 

1. A PROCESS OF PRODUCING DUAL TWIST NYLON YARN COMPRISING TWISTING NYLON YARN IN ONE DIRECTIN TO INSERT THEREIN A DESIRED NUMBER OF TURNS TWIST THROUGHOUT THE LENGTH OF THE YARN, NEXT TWISTING SAID YARN IN THE OPPOSITE DIRECTION WHILE WINDING UP SAID YARN AT A SUFFICIENTLY RAPID RATE TO AVOID SUBSTANTIAL REVERSE TWISTING FOR A GIVEN LENGTH OF THE YARN, AND THEN CONTINUING SAID REVERSE TWISTING AND WINDING UP SAID YARN AT A SUFFICIENTLY SLOW RATE TO IMPART AN OPPOSITE TWIST IN THE NEXT SUCCEEDING LENGTH OF YARN. 